CRA indicated that the qualifying costs of medically-assisted dying where there is compliance with the detailed procedures set out in the Criminal Code and various provincial rules would qualify for the medical expense tax credit. By implication, the costs of going abroad for the procedure might not qualify.
Neal Armstrong. Summary of 21 November 2017 CTF Annual Conference CRA Roundtable (Official Response), Q.16 under s. 118.2(2)(a).